PROCESS TO REMOVE DISSOLVED AlCl3 FROM IONIC LIQUID

ABSTRACT

Disclosed herein are processes in which precipitation permits removal of metal halides (e.g. AlCl 3 ) from ionic liquids. After precipitation, the precipitated metal halides can be physically separated from the bulk ionic liquid. More effective precipitation can be achieved through cooling or the combination of cooling and the provision of metal halide seed crystals. The ionic liquids can be regenerated ionic liquid catalysts, which contain excess metal halides after regeneration. Upon removal of the excess metal halides, they can be reused in processes using ionic liquid catalysts, such as alkylation processes.

CROSS-REFERENCE TO RELATED APPLICATION

The present invention is a divisional of U.S. patent application Ser.No. 13/830,750 filed Mar. 14, 2013, which is a divisional of U.S. patentapplication Ser. No. 12/324,570 filed Nov. 26, 2008, the contents ofwhich are hereby incorporated by reference in their entirety.

FIELD OF ART

The present disclosure relates to a process for removing metal halidesfrom an ionic liquid. In particular, the process involves precipitatingmetal halides out of a mixture comprising the ionic liquid and metalhalides. More particularly, the present disclosure relates to removingmetal halides (e.g. AlCl₃) from a regenerated ionic liquid catalystinvolving precipitating metal halides out of a mixture comprising theregenerated ionic liquid catalyst and metal halides.

BACKGROUND

An alkylation process, which is disclosed in U.S. Patent ApplicationPublication 2006/0131209 (“the '209 publication”), involves contactingisoparaffins, preferably isopentane, with olefins, preferably ethylene,in the presence of an ionic liquid catalyst to produce gasoline blendingcomponents. The contents of the '209 publication are incorporated byreference herein in its entirety.

An ionic liquid catalyst distinguishes this novel alkylation processfrom conventional processes that convert light paraffins and lightolefins to more lucrative products such as the alkylation ofisoparaffins with olefins and the polymerization of olefins. Forexample, two of the more extensively used processes to alkylateisobutane with C₃-C₅ olefins to make gasoline cuts with high octanenumbers use sulfuric acid (H₂SO₄) and hydrofluoric acid (HF) catalysts.

Ionic liquid catalysts specifically useful in the alkylation processdescribed in the '209 publication are disclosed in U.S. PatentApplication Publication 2006/0135839 (“the '839 publication”), which isalso incorporated by reference in its entirety herein. Such catalystsinclude a chloroaluminate ionic liquid catalyst comprising a hydrocarbylsubstituted pyridinium halide and aluminum trichloride or a hydrocarbylsubstituted imidazolium halide and aluminum trichloride. Such catalystsfurther include chloroaluminate ionic liquid catalysts comprising analkyl substituted pyridinium halide and aluminum trichloride or an alkylsubstituted imidazolium halide and aluminum trichloride. Preferredchloroaluminate ionic liquid catalysts include1-butyl-4-methyl-pyridinium chloroaluminate (BMP), 1-butyl-pyridiniumchloroaluminate (BP), 1-butyl-3-methyl-imidazolium chloroaluminate(BMIM) and 1-H-pyridinium chloroaluminate (HP).

However, ionic liquid catalysts have unique properties making itnecessary to further develop and modify the ionic liquid catalyzedalkylation process in order to achieve superior gasoline blendingcomponent products, improved process operability and reliability,reduced operating costs, etc. For example, as a result of use, ionicliquid catalysts become deactivated, i.e. lose activity, and mayeventually need to be replaced.

Alkylation processes utilizing an ionic liquid catalyst form by-productsknown as conjunct polymers. These conjunct polymers can deactivate theionic liquid catalyst by forming complexes with the ionic liquidcatalyst. Conjunct polymers are highly unsaturated molecules and maycomplex the Lewis acid portion of the ionic liquid catalyst via theirdouble bonds network system. As the aluminum trichloride becomescomplexed with conjunct polymers, the activity of the ionic liquidbecomes impaired or at least compromised. Conjunct polymers may alsobecome chlorinated and through their chloro groups may interact withaluminum trichloride and therefore reduce the overall activity of thecatalyst or lessen its effectiveness as a catalyst for the intendedpurpose such as alkylation. Deactivation of the ionic liquid catalyst byconjunct polymers is not only problematic for the alkylation chemistry,but also weighs in heavily on the economics of using ionic liquidsbecause they are expensive catalytic systems and their frequentreplacement will be costly. Therefore, commercial exploitation of ionicliquid catalysts during alkylation is impossible unless they areefficiently regenerated and recycled.

U.S. patent application Ser. No. 12/003,578 (“the '578 application) isdirected to a process for regenerating an ionic liquid catalyst whichhas been deactivated by conjunct polymers. The process comprises thesteps of (a) providing an ionic liquid catalyst, wherein at least aportion of the ionic liquid catalyst is bound to conjunct polymers; (b)reacting the ionic liquid catalyst with aluminum metal to free theconjunct polymers from the ionic liquid catalyst in a stirred reactor ora fixed bed reactor; and (c) separating the freed conjunct polymers fromthe catalyst phase by solvent extraction in a stirred or packedextraction column. The contents of the '578 application are incorporatedby reference herein in their entirety.

In order to provide regenerated ionic liquid catalyst, in the process ofthe '578 application, spent ionic liquid catalyst reacts with aluminummetal. If the spent ionic liquid catalyst is a chloroaluminate ionicliquid catalyst, such as catalysts disclosed in the '839 publication, itproduces aluminum trichloride (AlCl₃) as a byproduct. The AlCl₃byproduct can remain dissolved in the regenerated catalyst. Accordingly,it is necessary to separate the regenerated catalyst and the AlCl₃byproduct so that the regenerated catalyst can be recycled to thealkylation step.

Therefore, there is a need for an effective and efficient process forremoving metal halides from an ionic liquid catalyst, and, inparticular, a regenerated ionic liquid catalyst. In general, the processshould be simple and efficient enough to be used to separate any metalhalide from an ionic liquid.

SUMMARY

A process for removing metal halides from an ionic liquid is describedherein. In one embodiment, the process for removing metal halides froman ionic liquid comprises causing the metal halides to precipitate outof the ionic liquid. Enhanced precipitation can be caused by cooling.Cooling can also cause precipitation, which can provide metal halideseed crystals.

In another embodiment, a process for removing metal halides from anionic liquid comprises: a) feeding the ionic liquid comprising metalhalides to a vessel and providing metal halide seed crystals to providea mixture comprising ionic liquid, metal halides, and metal halide seedcrystals; b) cooling the mixture in the vessel to provide precipitatedmetal halides; and c) removing the precipitated metal halides from thevessel.

The ionic liquid may be an ionic liquid catalyst, which, after use, maybe regenerated in a manner that produces excess metal halides (e.g.AlCl₃) in the regenerated ionic liquid catalyst. Therefore, a processfor regenerating an ionic liquid catalyst is also disclosed herein. Theprocess includes: a) reacting an ionic liquid catalyst with aluminum toprovide a regenerated ionic liquid catalyst containing excess AlCl₃; b)precipitating the excess AlCl₃ from the regenerated ionic liquidcatalyst to provide precipitated excess AlCl₃; and c) removing theprecipitated excess AlCl₃ from the regenerated ionic liquid catalyst.

The ionic liquid catalyst and regenerated ionic liquid catalyst can beutilized in an alkylation reaction. Therefore, an alkylation process isfurther disclosed herein. The alkylation process includes: a) conductingan alkylation reaction with an ionic liquid catalyst to provide aproduct and a spent ionic liquid catalyst; b) reacting the spent ionicliquid catalyst with aluminum to provide a regenerated ionic liquidcatalyst and excess AlCl₃; c) precipitating the excess AlCl₃ from theregenerated ionic liquid catalyst to provide precipitated excess AlCl₃;d) removing the precipitated excess AlCl₃ from the regenerated ionicliquid catalyst; and e) recycling the regenerated ionic liquid catalystto reaction step a).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of the processwhereby metal halides are removed from an ionic liquid in acrystallization vessel.

FIG. 2 depicts particle size distribution of AlCl₃ crystals precipitatedin Example 5.

DETAILED DESCRIPTION Process for Removing Metal Halides from IonicLiquid

In one aspect, the present process is directed to removing metal halidesfrom an ionic liquid by precipitation. Accordingly, the present processinvolves causing the metal halides to precipitate out of the ionicliquid.

In one embodiment, the process involves cooling a mixture comprising themetal halides and ionic liquid to precipitate the metal halides out ofthe ionic liquid. Cooling facilitates precipitation of the metal halidesfrom the mixture. Upon cooling, the metal halides generally first formmetal halide seed crystals, which are extremely small, solid particlesof the metal halide. The reduced temperature then facilitatesprecipitation of additional metal halide onto the metal halide seedcrystals, causing the metal halide seed crystals to grow into larger,solid particles of precipitated metal halides. Accordingly, the processcan further involve cooling a mixture comprising metal halides and ionicliquid containing metal halide seed crystals.

It has been discovered that cooling and its associated formation of seedcrystals is particularly advantageous. As discussed above, coolingfacilitates precipitation. Cooling may even enhance precipitation rate.Seed crystals further facilitate precipitation and may increase theprecipitation rate.

As explained above, the metal halide seed crystals form naturally duringcooling of the mixture. However, additional metal halide seed crystalsmay be added to the mixture prior to cooling or during cooling. Addingseed crystals further enhances precipitation and results in largerparticles which are easier to separate.

The temperature to which the metal halide/ionic liquid mixture or metalhalide/ionic liquid/metal halide seed crystal mixture is cooled canvary. However, the temperature should be lower than the saturationtemperature for the particular metal halide to be removed from the ionicliquid. In one embodiment, the mixture can be cooled to a temperatureless than about 50° C. In another embodiment, the mixture can be cooledto about room temperature. In yet another embodiment, the mixture can becooled to a temperature less than about room temperature.

After the precipitated metal halides form, they can be physicallyseparated from the mixture and/or ionic liquid. Any known separationtechnique can be utilized depending upon time constraints, desiredthroughput, etc. For example, the precipitated metal halides can beseparated by decantation or filtration. Filtration allows for fasterseparation of the precipitated metal halides, because filtration doesnot require the precipitated metal halides to settle out of the bulkliquid like decantation. As such, one embodiment of the present processseparates the precipitated metal halides from the bulk liquid byfiltration.

The process can be either a batch process or a continuous process. Metalhalide seed crystals are generally present in a continuous process.

Ionic Liquids

As used herein, the term “ionic liquids” refers to liquids that arecomposed entirely of ions as a combination of cations and anions. Theterm “ionic liquids” includes low-temperature ionic liquids, which aregenerally organic salts with melting points under 100° C. and often evenlower than room temperature.

Ionic liquids may be suitable, for example, for use as a catalyst and asa solvent in alkylation and polymerization reactions as well as indimerization, oligomerization, acetylation, olefin metathesis, andcopolymerization reactions. The present embodiments are useful withregard to any ionic liquid catalyst.

One class of ionic liquids is fused salt compositions, which are moltenat low temperature and are useful as catalysts, solvents, andelectrolytes. Such compositions are mixtures of components, which areliquid at temperatures below the individual melting points of thecomponents.

The most common ionic liquids are those prepared from organic-basedcations and inorganic or organic anions. The most common organic cationsare ammonium cations, but phosphonium and sulphonium cations are alsofrequently used. Ionic liquids of pyridinium and imidazolium are perhapsthe most commonly used cations. Anions include, but are not limited to,BF₄—, PF₆—, haloaluminates such as Al₂Cl₇— and Al₂Br₇—, [(CF₃SO₂)₂N]⁻,alkyl sulphates (RSO₃ ⁻), carboxylates (RCO₂ ⁻) and many others. Themost catalytically interesting ionic liquids for acid catalysis arethose derived from ammonium halides and Lewis acids (such as AlCl₃,TiCl₄, SnCl₄, FeCl₃, etc.). Chloroaluminate ionic liquids are perhapsthe most commonly used ionic liquid catalyst systems for acid-catalyzedreactions.

Examples of such low temperature ionic liquids or molten fused salts arethe chloroaluminate salts. Alkyl imidazolium or pyridinium chlorides,for example, can be mixed with aluminum trichloride (AlCl₃) to form thefused chloroaluminate salts.

The ionic liquid from which the metal halides are subject to removal canbe any ionic liquid. The metal halide removal process as disclosedherein is not limited to regenerated ionic liquid catalysts or ionicliquid catalysts undergoing regeneration. For example, the metal halideremoval process may be used to remove metal halide contamination from anionic liquid.

Process for Regenerating an Ionic Liquid Catalyst

The present process is particularly useful when the ionic liquid is aregenerated ionic liquid catalyst. The present process works mosteffectively when the ionic liquid catalyst is fully regenerated, meaningthat the ionic liquid catalyst is substantially free from conjunctpolymers. The presence of conjunct polymers generally increases thesolubility of metal halides (e.g. AlCl₃) in ionic liquid thereby makingit difficult to precipitate out metal halides (e.g. AlCl₃). Accordingly,the present process is not nearly as effective when the ionic liquidcatalyst is only partially regenerated, meaning that the ionic liquidcatalyst still includes conjunct polymers such that it is notsubstantially free from conjunct polymers.

A used or spent ionic liquid catalyst can be regenerated by contactingthe used catalyst with a regeneration metal in the presence or absenceof hydrogen. The metal selected for regeneration is based on thecomposition of the ionic liquid catalyst. The metal should be selectedcarefully to prevent the contamination of the catalyst with unwantedmetal complexes or intermediates that may form and remain in the ionicliquid catalyst phase. The regeneration metal can be selected fromGroups III-A, II-B or I-B. For example, the regeneration metal can be B,Al, Ga, In, Tl, Zn, Cd, Cu, Ag, or Au. The regeneration metal may beused in any form, alone, in combination or as alloys.

Regenerating an ionic liquid catalyst in this manner can form excess,dissolved metal halide in the regenerated ionic liquid catalyst. It isthen necessary to remove this excess, dissolved metal halide from theregenerated catalyst before it can be recycled to the process utilizingthe ionic liquid catalyst and in need of regenerated catalyst. Moreover,the metal halide must be removed to prevent it from accumulating in theregeneration zone and other parts of the regeneration unit and causingplugging problems.

For example, deactivated, or at least partially deactivated,chloroaluminate ionic liquid catalyst can be reacted with aluminummetal, in the presence or absence of hydrogen, to regenerate thechloroaluminate ionic liquid catalyst. However, the reaction withaluminum metal can form excess, dissolved AlCl₃ in the regeneratedchloroaluminate ionic liquid catalyst. It is necessary to remove thisexcess, dissolved AlCl₃ prior to recycling the regeneratedchloroaluminate ionic liquid catalyst to, for example, an alkylationreaction.

Accordingly, the present disclosure further provides a process forregenerating an ionic liquid catalyst. Such regeneration processincludes the following steps: a) reacting an ionic liquid catalyst withaluminum to provide a regenerated ionic liquid catalyst containingexcess AlCl₃; b) precipitating the excess AlCl₃ from the regeneratedionic liquid catalyst to provide precipitated excess AlCl₃; and c)removing the precipitated excess AlCl₃ from the regenerated ionic liquidcatalyst.

As used herein, the term “excess AlCl₃” refers to the amount of AlCl₃produced during catalyst regeneration that is beyond its solubilitylimit in the ionic liquid catalyst at a particular temperature such thatit may precipitate out during the regeneration process.

As described above, the precipitating step can be accomplished throughcooling. More specifically, the precipitating step can involve coolingthe regenerated ionic liquid catalyst to precipitate excess AlCl₃ fromthe regenerated ionic liquid catalyst. This cooling step generallyprovides AlCl₃ seed crystals, which are the building blocks for largerparticles of precipitated excess AlCl₃ as described above. After theprecipitated excess AlCl₃ forms, it can be separated from the mixtureand/or ionic liquid. The temperatures and separation techniquesdiscussed above with regard to metal halides in general also apply toAlCl₃.

Process for Removing Metal Halides from an Ionic Liquid in aCrystallization Vessel

Yet another embodiment of the process involves removing metal halidesfrom an ionic liquid in a crystallization vessel. This embodiment can bebetter understood with reference to FIG. 1, which schematicallyillustrates this embodiment.

As shown in FIG. 1, the process includes feeding the ionic liquidcomprising metal halides 1 to a vessel 10 and providing metal halideseed crystals to provide a mixture 9 comprising ionic liquid, metalhalides, and metal halide seed crystals. The process further includescooling the mixture 9 in the vessel 10 to provide precipitated metalhalides and removing the precipitated metal halides from the vessel 10.Larger precipitated metal halides will eventually settle to the bottomportion 11 of the vessel 10 where they can exit the vessel 10, forexample, in an effluent stream 2 comprising such precipitated metalhalides.

The metal halide seed crystals can be provided by cooling, outsideaddition of metal halide seed crystals, or a combination thereof. Thesource of the metal halide seed crystals can depend upon whether theprocess is batch or continuous.

The cooling can be achieved by internally cooling the vessel contents(e.g. by a cooling jacket), externally cooling the vessel contents (e.g.by an external cooling loop), or a combination of both internally andexternally cooling the vessel contents.

The vessel 10 can be constructed such that it allows for removal of aleast a portion of the mixture, from an upper portion 12 of the vessel10; cooling the portion in a heat exchanger 4; and reintroducing theportion into the vessel 10. In FIG. 1, the portion that is removed fromthe mixture 9 is labeled as stream 3 and the cooled portion that isreintroduced into the vessel 10 is labeled as stream 7. Such an externalcooling loop 20 can provide certain advantages. Removing mixture fromthe upper portion 12 of the vessel 10 ensures a large amount of rathersmall metal halide particles, rather than large metal halide particles,enter the external cooling loop 20. Additional metal halideprecipitation occurs upon cooling of the removed portion. The smallmetal halide particles act as seed crystals such that metal halidedissolved in the ionic liquid precipitates onto these particles therebyproviding larger precipitated particles. Dissolved metal halideprecipitates onto these small metal halide particles rather than theheat exchanger walls. Furthermore, the reintroduction of the portion canagitate the mixture in the vessel and prevent seed crystals fromadhering the walls of the vessel.

The removed portion 3 can be filtered prior to cooling the removedportion. In FIG. 1, such a filtering step occurs in a filter 5.Filtering the removed portion 3 prevents any large metal halideparticles from entering the external cooling loop 20. The removedportion 3 subjected to filtration provides a filtered, removed portion6, which can then be cooled in the heat exchanger 4 to provide thecooled, removed portion 7, which is reintroduced to the vessel 10.

The reintroduction or recycle rate of the cooled, removed portion 7 intothe vessel 10 should be significant. For example, the cooled, removedportion 7 can be reintroduced into the vessel 10 at a rate between about5 and about 50 times the feed rate of the ionic liquid. In oneembodiment, the cooled, removed portion 7 can be reintroduced into thevessel 10 at a rate between about 10 and about 20 times the feed rate ofthe ionic liquid. Such a significant recycle rate is beneficial becauseit provides a high heat transfer coefficient, reduces the requiredtemperature change of the removed portion in the heat exchanger, andsweeps precipitate from the heat exchanger walls thereby reducingcoating of the heat exchanger walls.

Over time, the walls of the heat exchanger could become coated withprecipitated solid and will need to be cleaned. Therefore, it isdesirable to use a duplicate spare heat exchanger in the process forremoving metal halides from an ionic liquid. When coating of precipitateon the heat exchanger walls reduces heat transfer below a loweracceptable limit, flow of the removed portion to the heat exchanger canbe stopped and switched to the duplicate spare heat exchanger. Then thefirst heat exchanger can be cleaned. After cleaning, flow of the removedportion to the duplicate spare heat exchanger can be stopped and resumedin the first heat exchanger. In this manner, the process can run withoutinterruption.

To prevent deposition of precipitate on heat exchanger walls, they canbe treated to reduce nucleating sites. For example, the heat exchangerwalls can be polished or coated with a smooth material.

The feed of ionic liquid containing metal halides may also be pre-cooledbefore it enters the crystallization vessel. Pre-cooling the feed can beaccomplished by pre-mixing it with the cooled, removed portion orbringing the feed and the cooled, removed portion into close contact.

The vessel can be jacketed for cooling and/or heating. A cooling and/orheating jacket, shown in FIG. 1 as item 8, is useful to provideadditional cooling, adjust for any heat transfer to or from thesurroundings, maintain the vessel walls slightly warmer than itscontents to prevent precipitation on the vessel walls, and removeprecipitate from the vessel walls during cleaning.

The mixture 9 can be agitated by any known agitation method providedthat the agitation method does not destroy the metal halide seedparticles present in the mixture 9. For example, as shown in FIG. 1, animpeller 13 can agitate the mixture 9. Flow of the mixture 9 within thevessel 10 can also be regulated by any known flow regulation method. Forexample, as shown in FIG. 1, baffles 14 can regulate flow of the mixture9.

Alkylation Process

Another embodiment as described herein relates to an alkylation process,which utilizes the above-described metal halide (e.g. AlCl₃)precipitation process. The alkylation process first involves conductingan alkylation reaction with an ionic liquid catalyst to provide aproduct and a spent ionic liquid catalyst. The spent ionic liquidcatalyst is then reacted with aluminum to provide a regenerated ionicliquid catalyst and excess AlCl₃. The excess AlCl₃ is precipitated fromthe regenerated ionic liquid catalyst to provide precipitated excessAlCl₃, which is removed from the regenerated ionic liquid catalyst. Theregenerated ionic liquid catalyst is recycled to the alkylationreaction.

The following examples are provided to further illustrate the presentprocess and the advantages thereof. The examples are meant to be onlyillustrative, and not limiting.

EXAMPLES Example 1 Precipitation of AlCl₃ from Regenerated Ionic LiquidCatalyst

A 300 cc autoclave was charged with 50.60 gm spent ionic liquid catalyst(n-butyl pyridinium chloroaluminate) containing 24.3 wt % conjunctpolymers (acid soluble oils), 65 gm anhydrous normal hexane and 8 gmaluminum powder. The autoclave was sealed and heated to 100° C. for 90minutes to reactivate the catalyst. At the end of the heating period,the autoclave and its contents were cooled to room temperature. The toporganic layer (immiscible in the ionic liquid phase), containing theliberated conjunct polymers, was separated from the ionic liquid bydecantation. The ionic liquid phase was rinsed with additional hexane(2×50 ml) to ensure the removal of all liberated conjunct polymers. Theorganic rinses were combined and concentrated under a pressure on arotary evaporator to give 10.5 gm of conjunct polymers as reddishviscous oil. The ionic liquid layer (regenerated ionic liquid catalyst)was filtered in a glove box (oxygen and moisture free environment) toseparate the catalyst from excess aluminum powder. The regeneratedcatalyst was obtained in 33 gm as clear amber liquid. A small aliquot(10 gm) of the regenerated ionic liquid was hydrolyzed with excess waterand then extracted with hexane. The hexane layer was dried overanhydrous magnesium sulfate (MgSO₄), filtered and concentrated toretrieve any residual conjunct polymers that may have remained in thecatalyst. Only 0.07 gm conjunct polymers remained in the test sample.The remainder of the regenerated catalyst was transferred to a vial andkept in the glove box at room temperature. A few hours later, thecatalyst was checked and a fine off-white powder (aluminum trichloride)had settled at the bottom of the vial. The same observation was seen inseveral regeneration experiments.

Example 2 Recrystallization of Added AlCl₃ from Fresh Ionic LiquidCatalyst

To 20 gm of freshly-made ionic liquid catalyst (n-butyl-pyridiniumchloroaluminate) with an Al/N ratio of 2, 6.7 wt % AlCl₃ was added anddissolved by heating the catalyst to 100° C. The mixture was allowed tocool gradually to room temperature. The added AlCl₃ started to crash outof the catalyst soon after the cooling started and completelyprecipitated out within 2.5 hours.

Example 3 Recrystallization of Added AlCl₃ from Fully RegeneratedCatalyst

To 20 gm of fully regenerated n-butyl-pyridinium chloroaluminate ionicliquid catalyst containing <0.2 wt % conjunct polymers, 6.7 wt % AlCl₃was added and dissolved by heating the catalyst to 100° C. The mixturewas allowed to cool off gradually at room temperature. The added AlCl₃started to crash out of the catalyst soon after the cooling started andcompletely precipitated out within 4 hours. Accordingly, theprecipitation of added aluminum trichloride from the fully regeneratedcatalyst seems to behave similarly to the freshly-made catalyst.

Example 4 Recrystallization of Added AlCl₃ from Partially RegeneratedCatalyst

To 30 gm of partially regenerated n-butyl-pyridinium chloroaluminateionic liquid catalyst containing ˜2 wt % conjunct polymers, 9.8 wt %AlCl₃ was added and dissolved by heating the catalyst to 100° C. Themixture was allowed to cool off gradually at room temperature. The addedAlCl₃ started to precipitate out of the catalyst very slowly. It tookseveral hours to visibly see AlCl₃ precipitation at the bottom of thevial. It took nearly 72 hrs for ˜75% of the added AlCl₃ to precipitateout as determined by filtering the precipitated solids out.

In comparison to Example 3, Example 4 shows that the process forremoving metal halides from an ionic liquid as described herein is notas useful and efficient with partially regenerated ionic liquidcatalyst. Rather, the process is more useful and efficient with fullyregenerated ionic liquid catalyst.

Example 5 Continuous Crystallization of AlCl₃ from Regenerated IonicLiquid Catalyst

Crystallization of AlCl₃ from regenerated catalyst was performed in acontinuous crystallization unit. An ionic liquid solution containing 0.1wt % conjunct polymers (CP) and 6 wt % of AlCl₃ was prepared prior tothe experiment by adding 33.2 g of AlCl₃ powder with 99.999% purity into350 ml of regenerated ionic liquid catalyst. The prepared ionic liquidsolution was then charged into the continuous crystallization unit,which consisted of a 200 ml ChemGlass crystallizer equipped with a 1.5inch diameter overhead stirrer and heating/cooling jacket, a tubingpump, and a 250 ml flask as catalyst reservoir above a heating mantle.Tubes connecting these items were wrapped with heating tape. A Lasentec®FBRM probe manufactured by Mettler-Toledo was used for particle sizedistribution measurement.

The crystallization experiments were conducted at 4° C. and atmosphericpressure with overhead stirring at 400 RPM. From the bottom of thecrystallizer, a small stream of the slurry containing AlCl₃ crystals andionic liquid solution was continuously withdrawn and pumped by thetubing pump to the catalyst reservoir. AlCl₃ crystals in this streamwere dissolved back into the ionic liquid solution by heating the tubesand the catalyst reservoir to 180° F., which was well above thetemperature needed to dissolve 6 wt % AlCl₃ in ionic liquid. This ionicliquid solution which was free of AlCl₃ crystals was fed back to thecrystallizer as feed. The recirculation flow rate was carefullycontrolled by the pump and resulted in a residence time of 6 hours inthe crystallizer.

The particle size distribution of the AlCl₃ crystals was monitored andrecorded continuously by the FBRM probe. FIG. 2 shows the particle sizedistribution measured by the FBRM probe when the system reached a steadystate.

Although the present processes have been described in connection withspecific embodiments thereof, it will be appreciated by those skilled inthe art that additions, deletions, modifications, and substitutions notspecifically described may be made without departing from the spirit andscope of the processes as defined in the appended claims.

That which is claimed is:
 1. An alkylation process, comprising: a)conducting an alkylation reaction with an ionic liquid catalyst toprovide a product and a spent ionic liquid catalyst; b) reacting thespent ionic liquid catalyst with aluminum to provide a regenerated ionicliquid catalyst and excess dissolved AlCl₃; c) precipitating the excessdissolved AlCl₃ from the regenerated ionic liquid catalyst to provideprecipitated excess AlCl₃; d) removing the precipitated excess AlCl₃from the regenerated ionic liquid catalyst; and e) recycling theregenerated ionic liquid catalyst to reaction step a).
 2. The processaccording to claim 1, further comprising isolating the product from thealkylation reaction.
 3. The process according to claim 1, furthercomprising removing the precipitated excess AlCl₃ by filtration.
 4. Theprocess according to claim 1, further comprising removing theprecipitated excess AlCl₃ by decantation.
 5. The process according toclaim 1, wherein the mixture is cooled to a temperature less than about50° C. to precipitate the excess dissolved AlCl₃.
 6. The processaccording to claim 1, wherein the mixture is cooled to about roomtemperature or to less than about room temperature to precipitate theexcess dissolved AlCl₃.
 7. The process of claim 1, wherein the ionicliquid catalyst is n-butyl pyridinium chloroaluminate.
 8. An alkylationprocess, comprising: a) conducting an alkylation reaction with an ionicliquid catalyst to provide a product and a spent ionic liquid catalyst;b) reacting the spent ionic liquid catalyst with aluminum to provide aregenerated ionic liquid catalyst and excess dissolved AlCl₃; c) feedingthe regenerated ionic liquid catalyst and dissolved AlCl₃ to a vesseland providing metal halide seed crystals to provide a mixture comprisingregenerated ionic liquid catalyst, dissolved AlCl₃, and metal halideseed crystals; d) cooling the mixture in the vessel to provideprecipitated AlCl₃; e) removing the precipitated AlCl₃ from the vessel,and f) recycling the regenerated ionic liquid catalyst to reaction stepa).
 9. The process according to claim 8, further comprising removing theprecipitated excess AlCl₃ by filtration.
 10. The process according toclaim 8, further comprising removing the precipitated excess AlCl₃ bydecantation.
 11. The process according to claim 8, wherein the mixtureis cooled to a temperature less than about 50° C. to precipitate theexcess dissolved AlCl₃.
 12. The process according to claim 8, whereinthe mixture is cooled to about room temperature or to less than aboutroom temperature to precipitate the excess dissolved AlCl₃.
 13. Theprocess of claim 8, wherein the ionic liquid catalyst is n-butylpyridinium chloroaluminate.
 14. The process according to claim 8,further comprising isolating the product from the alkylation reaction.